PROPAGATION OF DAMSELFISH (POMACENTRIDAE) COURTSHIP SOUNDS

Many damselfishes perform a courtship behavior known as the signal jum p, in which they rise in the water column and then rapidly swim downwa rd while producing a pulsed sound. Pulsed sounds produced during the s ignal jump of the damselfish Dascyllus albisella were analyzed to dete rmine whether they were correlated with the signal jump distance or sp eed, and how they changed with propagation. No statistical relationshi p was found between signal jump speed or distance with the number of p ulses, pulse period, or change in the peak frequency of pulses in a ca ll. If echoes were present in the sound, the change in echo delay woul d likely have been too small for damselfish to detect. Sounds attenuat ed with distance such that the signal-to-noise ratio decreased from 17 -25 dB at 1 to 2 m to 5-10 dB at 11 to 12 m. It is unlikely that D. al bisella can detect sounds at or beyond 11-12 m from the sound source, based on noise masking data from other fishes. Pulse period is least a ffected by propagation when compared to peak frequency, pulse duration , interpulse interval, and coefficient of variation of pulse amplitude s within a call. These results suggest that the sound produced during the signal jump functions over short distances and that the pulse peri od provides the most reliable basis for signal identification. (C) 199 7 Acoustical Society of America.